Let us turn the Holy Grail of philosophy into a testable question.
Find for all of reality with prior evidence or proof all local examples of it within reality (as it comes to humans). Now use logic and reduction to math and science and keep the strong AND from logic and only get positive results.
The last one is the joker:
Your overall theory of everything can't yield relativism.
Here is how:
You: Here is the ToE, follow it,
because you can't do it differently. (That is the testable part)
Me: No!
The test is as always that there is no relativism at all.
You can't reduce all human behavior down to the same with the logical AND.
So here it is from within philosophy as with logic and ontology combined:
"It is impossible that the same thing belong and not belong to the same thing at the same time and in the same respect." Aristotle
Now you can't reduce differences in human behavior away if they disagree and you can't use logic on two humans, if they disagree. How? Because they are not the same thing!!!
It is that simple!
That is it. We can go on with logic as much as you like and if I can do my life differently that you can do yours, I will do so, when it comes to this.
The actual everyday life falsification of your idea, is that humans will continue to disagree with you.
I am a general skeptic and I know how to falsify the ToE for all human behavior. I just disagree.
Agrippa the Skeptic - Wikipedia
The first mode of falsification as per Agrippa the Skeptic of a ToE is simple:
The uncertainty demonstrated by the differences of opinions among philosophers and people in general.
You have nothing but an opinion and I have a different one. Nice, ain't it.
You really need to study the basics and apply them to all human behavior as observed by field observation. You know, look at humans in the will. Like as an Internet forum and observe that they can actually disagree and both can get away with it.
Relativism in humans are a result of the effect of the replication of the fittest gene with a social species like humans. We do the 4Fs in biology within the species and we compete for resources, power and prestige.
Now if humans cease to be humans, then yes, there might be a possible ToE. But as long as our biology stays fundamentally the same, humans will continue to answer "No!" to your idea.
Subjectivism and relativism in humans are a result of biology. Good luck trying to change that.
Sorry, I know, it is a bummer. But if you had checked the knowledge already out there, you wouldn't claim, what you claim.